Process for protecting the surface of an image

ABSTRACT

IMAGES ARE PROTECTED BY LAMINATING A FILM OVER THE SURFACE OF THE IMAGE. A PRESSURE ROLLER PROVIDED WITH PROJECTIONS IS USED TO IMPROVE THE BONDING OF THE FILM TO THE IMAGE SUPPORT.

March 26, 1974 MASAAKI TAKIMOTO ETAL 3,799,827

PROCESS FOR PROTECTING THE SURFACE OF AN IMAGE Filed Dec.l 23, 1971 FIG. 3c F/G. 3d

SEIJI MATSUMOTO- BY/dw@ M ATTORNEY FUnited States Patent O U.S. Cl. 156-219 4 Claims ABSTRACT OF THE DISCLOSURE Images are protected by laminating a film over the surface of the image. A pressure roller provided with projections is used to improve the bonding of the film t the image support.

-BACKGROUND OF THE INVENTION This invention relates in general to imaging. More specifically the invention relates to the protection and fixing of images.

In a number of relatively new imaging systems images are formed of finely divided particulate material. Exemplary of these new systems are xerography and photoelectrophoresis. Because the images are made up of more or less loosely held particulate material these images are subject to damage whenever they are handled. Several methods have been proposed for fixing these images. Among the methods are laminating a transparent sheet over the particles or providing a film-forming liquid layer over the image. Also proposed are adhesive layers or, where liquids are used during image formation, binder materials may be dissolved therein which upon removal of the liquid bind the particles. Further techniques include using particles which are fusible or supplying a fusible substrate for the particles which on application of heat or solvent will cause the particles to adhere to the substrate. Of course it is not always possible to provide fusible toner or substrate materials. For example in photoelectrophoresis as shown in U.S. Pat. 3,384,566 to H. E. Clark often pigment materials are used which cannot be fused. A further problem with many of the above processes is that they require liquid handling and often require an extended drying period which may be unsatisfactory for rapid image production.

Laminating a film over the image overcomes a number of the problems in image fixing and protecting in `that it assures that all particles in the imageV are permanently fixed thereon. It can be a completely dry system applicable to high speed operation and it provides aypleasing glossy appearance to the final image. It has been found however that on certain materials it is diicult to attach laminates securely. The problem is particularly severe when the substrate on which the image is formed is relatively brittle. An example of a material on which lamination has not been entirely satisfactory is zinc oxide binder plates. It has been found that the photoconductive layer and the laminated film often separate.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a system for fixing and protecting a particulate image which overcomes the above noted disadvantages.

It is another object of this invention to provide' an improved laminating system. a

ice

It is another object of this invention to provide a system for laminating which relatively improves the bonding between the laminations.

The above objects and others are accomplished in accordance with this invention by forming a particulate image on a flexible substrate. The image bearing substrate is then brought into contact with a transparent film having an adhesive layer, for example, a layer of a material which can be rendered adhesive by application of heat. The transparent -film is rendered adhesive, for example by application of heat and the heated film is pressed to the image bearing substrate by pressure rollers. The pressure roller on the transparent film side of the lamination is provided with small raised areas. The opposing roller is rigid. Sufficient force is exerted to cause the image bearing substrate to be indented by the projections, the film being forced into the indentations. The film is then allowed to cool providing a firm, strongly adhering bond betweenthe transparent film and the image bearing substrate. Alternatively, the adhesive layer may be made tacky by contact with a solvent.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved method of Ifixing and protecting a particulate image will become apparent upon consideration of the detailed disclosure of the invention especially when taken in conjunction with the accompanying drawings wherein: FIG. 1 is a side sectional view of a simple exemplary system for laminating in accordance with the present invention.

FIG. 2 illustrates a second embodiment using additional rollers.

FIG. 3 shows examples of shapes of projections which may be used on the pressure roller.

Referring now to FIG. -1 there is seen image bearing member generally designated 1 which in this exemplary instance isA paper 2 overcoated with a layer 3 of photoconductive zinc oxide in a resin binder. Layer 3 is the support-.for the particulate image not shown which it is desired to fix. Plastic film 4 is provided with a layer 5 of material which on application of heat becomes adheSi-ve. Pressure roller 6 having projections 7 on its outer surface is heated by heating element 11. Projections 7 may be, for example, raised dots, pyramids, cones, lines, a screen or other suitable shape. Substrate supporting roller 8 is metal or hard rubber and should be relatively rigid. Softer materials are not as effective. 4Roller 8 may be provided with depressions matching the projections on roller 6 which assist the projections in causing a cave-in of the film and the image substrate.

In operation, substrate 1 having a particulate image on, its top surface and film 4 with adhesive layer S on its surface aredrawn into the nip between rollers 6 and 8 by rotation of rollers 6 and 8 so that adhesive layer 5 contacts the image and image substrate. Heating element 11 is used to heat roller 6 so that layer 5 is heated and thus rendered adhesive. The pressure rollers 6 and 8 are pressed firmly together so that where projections 7 contact the film both the -film and at least the surface of the image bearing substrate 1 are deformed with film 4 being pressed into substrate 1. The lamination is then allowed to cool providing a permanent, strongly adhering bond.

' The clear plastic laminating lm on which the adhesive y layer is coated may comprise any suitable material.

3 l Typical plastic materials include polyethylene; polypropylene; polyethylene terephthalate; polyvinyl chloride;

polyvinylidene chloride; cellulose acetate; cellulose acetate" butyrate; polycarbonate; cellophane and mixtures thereof.

The adhesive layer may be adhesive at room temperature or may preferably be adhesive at elevated temperatures to ease handling. Preferably the materials are solid at room temperatures and are capable of softening and becoming adhesive at reasonably elevated temperatures. A preferred material is made up of a binder material and a thermo-solvent for the binder. A thermosolvent is a material which melts at slightly aboveroom temperature and acts as a solvent for the binder. This structure provides a sharper tackifying point than is otherwise possible.

Any suitable mixture of binder resin and thermosolvent may be used in the process of this invention. Optimum results have been obtained with mixtures of Vinylite VYNS, a vinyl chloride-vinyl acetate copolymer, available from Union Carbide Corporation, .and Santolite MHP, an aryl sulfonamide-formaldehyde copolymer available from Monsanto; polyvinylpyrrolidone-vinylacetate copolymer and Santolite MHP, a Vinylite VYHO and Aroclor 4465, a blend of chlorinated biphenyls and chlorinated triphenyls. Best results have been obtained with, and therefore, the preferred formulation is, a mixture of 1 parts by weight Exon-470, a vinylchloridevinylacetate copolymer available from Firestone, about 1 part by weight Santicizer 1-H, a sulfonimide resin available from Monsanto, dissolved in about parts acetone. This formulation is preferably coated to a thickness of about 0.5 mil and dried. Any other suitable mixture of binder resin and thermo-solvent may be used. Typical binder resin materials include polyethylenes, polystyrenes, copolymers of vinylchloride and vinylacetate, copolmers of vinylpyrrolidone and vinylacetate, polyvinyl methacrylates, polyvinyl propylene, polyvinylchloride, cellulose acetate, chlorinated rubber, and mixtures and copolymers thereof. Typical thermo-solvents having melting points slightly above room temperature include (with melting temperatures in parentheses) triphenyl phosphate (48 C.); dicyclohexyl phthalate (63 C.); diphenyl phthalate (69 C.); Aroclor 5442 (46-52 C.) a chlorinated polyphenyl available from Monsanto; Santicizer 3 (58 C.) N-ethyl-p-toluenesulfonamide, available from Monsanto; Santolite MHP (62 C.) a sulfonamideformaldehyde resin available from Monsanto; Santicizer l-H (82 C.) N-cyclohexyl-p-toluene-sulfonamide, available from Monsanto; acenaphthene (94 C.) acetanilide (113 C.); o-acetoaceto-toluidide (105 C.); o-acetotoluidide (101 C.); o-chloroacetoacetanilide (103 C.); 2-chloro-4-nitroaniline (106 C.); p-dibromobenzene (87 C.); p,pmethylenedianiline (93 C.); alphanaphthol (95 C.); beta-naphthol (85 C.); 2-naphthylamine (110 C.); m-nitroaniline (112 C.); 4nitrobi phenyl (97 C.); sorbitol hexeacetate (98 C.); 2,4 toluenediamine (97 C.); and mixtures thereof.

Any suitable ratio of binder to thermo-solvent may be used. Ratios of from 0.5 to 4 parts binder resin for each part of thermo-solvent may be used. For optimum results, a ratio of binder resin to thermo-solvent of about 1:1 is preferred. This ratio may vary depending upon the particular binder resin and thermo-solvent selected. The thickness of the thermo-adhesive layer should preferably be between 0.1 and 4 mils. The optimum balance between effective transfer and economy of materials has been found to occur with a thermo-adhesive thickness of about 0.5 mil.

Referring now to FIG. 2 there is seen a preferred embodiment for using heat tac-kiiable layers. Additional rollers 9 and 10 are used to insure that thermo-,adhesive layer S is rendered completely tacky before being pressed by rollers 6 and 8. Rollers 6 and 8 may optionally be heated.

`Where the image 'substa'rte'is a photoconductor and liquid developer is used the adhesive layer 5 may be chosenv to be made adhesive by the action of residual developer liquid. Por example, for liquid developers the liquid carrier in which the particulate toner material is suspended may be a solvent for layer 5. The carrier liquid which remains on the image immediately after image formation can be used to partially dissolve the surface of the laminating sheet coated with the adhesive causing the adhesive to become tacky.

The tackfable layer on the transparent plastic sheet may compirse any suitable material which is at least partially soluble in the carrier liquid used to suspend the particles during development. The carrier liquid may comprise any suitable substantially insulating liquid. Typical carrier liquids include decane, dodecane, N-tetradecane, Sohio Odorless Solvent 3440 (a kerosene fraction available from the Standard Oil Company of Ohio), 'Isopar-G (a long chain saturated aliphatic hydrocarbon available from Humble Oil Company of New Jersey), and mixtures thereof. Typical materials which have been found to be suitably tackiiied by long chain hydrocarbon carrier liquids include Staybelite Ester 10, a glycerol triester of 50 percent hydrogenated -wood resin, available from the Hercules yPowder Company; Piccotex 100, a copolymer of alpha methyl styrene and vinyl toluene, available from Pennsylvania Industrial Chemical Company; Piccopale H-2, a hydrocarbon resin available from Pennsylvania Industrial Chemical Company; Marbon 1100 T, a linear hydrocarbon polymer available from Marbon Chemical Co.; Piccolite SL15, a terpene lpolymer available from Pennsylvania Industrial Chemical Company; Marbon 9200, a styrene copolymer available from Marbon Chemical Co.; and mixtures thereof. In general, low molecular weight polymers are preferred since these have the desired solubility in the usual aliphatic hydrocarbon carrier liquids. yOf course, where other insulating carrier liquids are used, other materials which have the desired partial solubility may be used in layer 5.

Referring now to FIG. 3 there is shown examples of shapes the projections may take. FIG. 3a and e are cones or pyramids, FIG. 3b is a cylinder or -a rectangle, FIG. 3c is rounded, FIG. 3d is a rectangle or cylinder with rounded corners. The projections are preferably about 0.1 to 1.5 mm. high and about 0.1 to 2 mm. in cross section at their base. The angular projections such as in FIG. 3a, c or e have a pitch preferably of about 0.2 to 3.0 mm. The projections may be randomly or regularly positioned; it is preferred however that in any 10 mm. diameter circular area on the surface of the roller that there be at least two projections. The clear plastic film may be colored for special eifect or may be translucent. lIt may also contain ultraviolet-absorbing materials for protecting the image from fading.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

,What is claimed is:

1. A method of fixing images which comprises pressing an image bearing substrate and a laminating ilm together between a first roller having projections, said projections being from about 0.1 to about 1.5 mm. in height and from about 0.1 to about 2.0 mm. in cross section at the base of each of said projections said projections being present on the surface of said first roller in suiiicient number so that any 10 mm. diameter surface area of said roller which is in pressing contact contains at least two of said projections, the pressure applied between said rollers being suicient to cause the projections to deform said film and said substrate.

l 2. I'he method of claim 1 wherein said laminating film includes a layer which can be rendered adhesive by application of heat and including the additional step of heating said layer.

5 3. The method of claim 1 wherein said laminating lm 3,674,591 includes a layer which can be rendered adhesive by sol- 3,386,874 vent and including the additional step of contacting said 3,079,272 layer with a solvent. 3,427,242

4. The method of claim 1 wherein said substrate is a photoconductive member.

Boyd 156-272 Gros 156-220 Greig 96--1 lLY X Mihajlov 96-1.3 X

5 ALFRED L. LEAVHT, `Primary Examiner D. A. SIMMONS, Assistant Examiner References Cited UNITED STATES PATENTS 3,654,022 3,549,447 12/1970 Bresnick 156-230 Us. c1.x.R.

4/1972 Diest s 15e-220x 10 961R; 156-220, 307

UNITED STATES PATENT oFFICE V CERTIFICATE r0F CORRECTION y Patent No. 3.799, 827 Dated March 26, 1974 Inventods) Masaaki Takimoto and Seiji Matsumoto I It is certified that error appears in the above-identified patent j and that said Letters Patent are hereby corrected as shown below:

Column 4, line l "substarte" should read substrate Column 4, line l2 "compirse" should read comprise Claim l, line lO after "projections insert and a second roller Signed andsealed this 8th day of October 1974.

V(SEAL) Attest:

l'McCoY M. GIBSON JR, C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM {DO-1050 (10-69) USCOMM-DC 603764269 w u,s. sovERNMzNT Pnmrmc orrlcs: Isn o-ase-azu, 

